Johann W. Kolar

Bio: Johann W. Kolar is an academic researcher from ETH Zurich. The author has contributed to research in topics: Rectifier & Three-phase. The author has an hindex of 97, co-authored 965 publications receiving 36902 citations. Previous affiliations of Johann W. Kolar include Alstom & Infineon Technologies.

Analysis and practical relevance of CM/DM EMI noise separator characteristics

Abstract: This work investigates sources of measurement errors that result for common mode/differential mode (CM/DM) separators in a practical measurement environment, with a particular focus on the recently ...

Letters to the Editor Comparison of 3-Phase Wide Output Voltage Range PWM Rectifiers

Abstract: A three-phase buck + boost pulsewidth modulation (PWM) rectifier with a three-switch buck-type rectifier input stage and an inte- grated dc/dc boost converter output stage, and a three-phase boost + buck PWM rectifier system formed by series connection of a boost-type rectifier input stage (Vienna Rectifier) and a dc/dc buck converter output stage are presented and comparatively evaluated. Both systems are characterized by sinusoidal input current and wide output voltage control range. The comparison is for 6 kW rated output power at 400 Vrms line-to-line input and variable output voltage 200 V ,..., 600 V and identifies the buck + boost approach as significantly superior regarding the overall efficiency, the volume and weight of the passive power components, and the overall system complexity.

Editorial: Special Issue on High-Frequency-Link Power-Conversion Systems, 2014

Abstract: The overall objective of this IEEE Power Electronics Society (PELS) Special Issue on high-frequency-link power-conversion systems is, therefore, to bring out the highlights of the ongoing world-wide activities in this area of advanced research to expose, analyze, and resolve the critical research and developmental challenges. The Special Issue received a total of 132 manuscripts for review considerations of which 35 manuscripts have been accepted for final publication. These publications encompass all four broad categories of high-frequency-link power-conversion systems (i.e., dc/ac, ac/dc, ac/ac, and dc/dc converters) with broad applicability in the following areas of application: photovoltaic energy, wind energy, electric vehicles, fuel-cell energy, energy storage, uninterruptible power systems, motor drives, high-frequency-ac power distribution systems, high-voltagedirect- current transmission, active load emulator, smart/micro grid, solid-state transformers, induction heating, railway traction drive, pulsed power, plug-in hybrid-electric-vehicle, battery charging, inductive power transfer. The contributions of the articles compiled in this special issue are multifold encompassing topologies with plurality of stages and/or levels, modulation, loss-mitigating switching, high-frequency magnetics, control, modeling, switched-capacitor power conversion, power-factor correction, and broad overviewof the Special-Issue subject area.

Contributions to an ultra-high temperature (250°C/500°F) bearingless pump

Abstract: The semiconductor industry demands for pumps which handle aggressive fluids at very high temperatures, as this is an important step towards higher process speeds and increased yield in semiconductor etching applications. This paper presents the thermal, electrical and mechanical design of a bearingless pump for operating temperatures of up to 250 ° C without active cooling. A detailed thermal analysis of the machine is presented which allows for the prediction of the thermal stress of critical components. The machine design is based on the prediction of the internal temperatures and hydraulic specifications of the pump. Furthermore, a hallsensorless, observer-based, control of the rotor angle is presented. The necessity for this control scheme arises from the high temperatures that prevent the usage of conventional angle measurement systems.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Multilevel inverters: a survey of topologies, controls, and applications

Abstract: Multilevel inverter technology has emerged recently as a very important alternative in the area of high-power medium-voltage energy control. This paper presents the most important topologies like diode-clamped inverter (neutral-point clamped), capacitor-clamped (flying capacitor), and cascaded multicell with separate DC sources. Emerging topologies like asymmetric hybrid cells and soft-switched multilevel inverters are also discussed. This paper also presents the most relevant control and modulation methods developed for this family of converters: multilevel sinusoidal pulsewidth modulation, multilevel selective harmonic elimination, and space-vector modulation. Special attention is dedicated to the latest and more relevant applications of these converters such as laminators, conveyor belts, and unified power-flow controllers. The need of an active front end at the input side for those inverters supplying regenerative loads is also discussed, and the circuit topology options are also presented. Finally, the peripherally developing areas such as high-voltage high-power devices and optical sensors and other opportunities for future development are addressed.

Recent Advances and Industrial Applications of Multilevel Converters

Abstract: Multilevel converters have been under research and development for more than three decades and have found successful industrial application. However, this is still a technology under development, and many new contributions and new commercial topologies have been reported in the last few years. The aim of this paper is to group and review these recent contributions, in order to establish the current state of the art and trends of the technology, to provide readers with a comprehensive and insightful review of where multilevel converter technology stands and is heading. This paper first presents a brief overview of well-established multilevel converters strongly oriented to their current state in industrial applications to then center the discussion on the new converters that have made their way into the industry. In addition, new promising topologies are discussed. Recent advances made in modulation and control of multilevel converters are also addressed. A great part of this paper is devoted to show nontraditional applications powered by multilevel converters and how multilevel converters are becoming an enabling technology in many industrial sectors. Finally, some future trends and challenges in the further development of this technology are discussed to motivate future contributions that address open problems and explore new possibilities.